Conventional irrigation experiments and rainfall distribution‐yield studies have indicated that insufficient water during flowering and pod‐fill stages frequently limits yields of soybeans (Glycine max (L.) Merr.). In this 3‐year experiment, field plot covers were used to control rainfall and water stress was imposed on plants at various stages of growth to determine more specifically the critical periods for irrigating soybeans for maximum yields. Soil water regimes ranged from a limited supply (10% available soil water) to adequate water (50% available) during the entire growing season. More bean production was obtained from water applied after full bloom than earlier. The pod‐fill stage, from August 15 to September 20 for ‘Bragg’ soybeans at Thorsby, Alabama, was the critical time for adequate water for maximum yields. Yields from adequately watered soybeans were 540 to 1,040 kg/ha, or 24 to 55%, greater than where water was limited throughout the growing season. Highest yield obtained under the best water regime was 3,320 kg/ha. Conditions limiting yields were not obvious.

The purpose of this study was to determine the efficacy of several milk substitutes compared to whole milk in maintaining the viability of human periodontal ligament (PDL) cells on avulsed teeth. PDL cells were obtained from freshly extracted, healthy third molars and cultured in Eagle's minimal essential media (EMEM). The cells were plated onto 24-well culture plates and allowed to attach for 24 h. EMEM was replaced with refrigerated whole milk (positive control), reconstituted powdered milk, evaporated milk, or one of two baby formulas (Similac or Enfamil). Tap water served as the negative control. Tissue culture plates were incubated with the experimental media at 37 degrees C for 1, 2, 4, or 8 h. Cell viability was determined by a cell proliferation assay (CellTiter 96 AQ Assay), with absorbance read at 450 nM. A two-way ANOVA (p < 0.001) indicated that at 1 h there was no difference in the effect on PDL cell viability between any of the materials and whole milk. At 2 h, Enfamil and Similac performed significantly better than whole milk, whereas evaporated milk performed worse. At 4 h, Enfamil performed better than whole milk, whereas all other milk substitutes performed worse. At 8 h, all substitutes performed worse than whole milk. These results suggest that Enfamil, which is supplied in powder form that does not require special storage and has a shelf life of 18 months, is a more effective storage medium for avulsed teeth than pasteurized milk for at least 4 h.

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Synopsis Grass yields responded strongly to yearly applications of up to 400 pounds of K per acre and at a slower rate to even higher applications. With 800 pounds of K, exchangeable soil K content was maintained and two‐thirds of the applied K was recovered in the forage. At the 1600‐pound rate, recovery in the forage was reduced but exchangeable soil K content was increased. K content of the forage increased with rates and with yields.

An experiment was conducted under field conditions to study the movement and recovery of N15‐enriched nitrogen fertilizer added to soil in the forms of NaNO3 and (NH4)2SO4. The plots consisted of the soil mass inside cylinders 30 or 60 cm in diameter, which were pressed into the soil to a depth of 45–60 cm. These plots were either seeded to sudangrass (sorghum sudanense) or left uncropped. The plant tops, roots, and the soil, by 15‐cm layers, were analyzed for total N and excess N15 content. Recovery of added N15 from the 32 plots ranged between 96.3 and 101.8%, and averaged 99.0%. There was no significant difference in recovery of the fertilizer N due to the percent of excess N15 in the fertilizer, size of plot, exposure to natural rainfall, cropping, N source, or the time of application of the fertilizer. Wide variation in recovery of excess N15 occurred with core sampling and it was found necessary to remove, weigh, mix and subsample the entire soil mass from within the rims. The small amounts of unrecovered N were probably due to procedural errors in the field and laboratory, and leaching and root growth beyond the sampling zone. There was no indication of any N loss in the gaseous form. The fate of applied fertilizer N was followed under field conditions using N15‐enriched nitrogen fertilizer applied to the soil in situ enclosed by large steel cylinders. Total recovery of the fertilizer N from these experiments after 8 weeks ranged from 88 to 96%, but dropped as low as 77% after 10 months. Recovery of the fertilizer N was greater from an ammonium source than from nitrate. Retter recovery of fertilizer was obtained when the plots were cropped to sudangrass rather than left fallow. Doubling the rate of application of the fertilizer N from 336 to 672 kg/ha did not affect percent of total recovery. The 4 to 12% of fertilizer N unrecovered after 8 weeks appears to be due to a loss in the gaseous form, since special precautions were taken to restrict leaching and to eliminate errors in sampling and analysis.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAtmospheric concentrations of CO 2 have risen since the beginning of the industrial revolution, primarily as a consequence of fossil fuel combustion for energy production and other industrial activities. Recognizing the challenge imposed by the potential for climate change, recent initiatives by various governments and by energy producers target a significant reduction in the intensity of CO 2 emissions into the atmosphere. A major mitigation strategy for reducing the intensity and amount of CO 2 emissions into the atmosphere is CO 2 capture and sequestration, of which geological sequestration is a major component. Although enhanced oil recovery operations have the lowest capacity of all options for geological CO 2 sequestration, they are most likely to be implemented first because of the additional economic benefit that will help offset the cost of CO 2 sequestration.Assuming that the pore space previously occupied by the produced oil can be backfilled with CO 2 , a methodology has been developed for the identification and screening of oil reservoirs that are suitable for CO 2 flooding and for estimating their CO 2 sequestration capacity at depletion, as well as under enhanced oil recovery.